I have a BCD996P2 in the car. This is the setup that I have found works for my situation.
I have a group & quick key for each county I most often drive through (5 groups), several groups for event & statewide, a group for MSP, and several other miscellaneous groups.
If I am going to leave the 5 programmed counties, I create a separate system for the other counties and copy-paste the statewide/event TGs into the new system. Or, more commonly, I take my BCD436HP along.
Several things I do to save space
I do not program any RIDs.
I keep ID Search enabled, and Permanent L/O any TGs that are outside my listening area as they pop up.
I do not program any full-time encrypted TGs. Instead I Permanent L/O each one as they pop up so they do not slow down scanning.
I do not program any paging groups. I still hear them since ID Search is enabled, and the department and address given over the air provide enough context.